Low Potassium: The Silent Metabolic Match in HFpEF

Key Takeaway: In patients with heart failure with preserved or mildly reduced ejection fraction (HFpEF/HFmrEF), low potassium levels appear to be associated with an increased risk of developing new-onset type 2 diabetes. This finding underscores the importance of meticulous electrolyte monitoring in heart failure, not only to prevent dangerous cardiac rhythms but also to potentially guard against metabolic disease.

When the Heart and Pancreas Share a Common Vulnerability

Picture a 67-year-old woman with heart failure. Her heart’s pumping function is reasonable—an ejection fraction of 48%—but because her heart muscle has stiffened, it struggles to relax and fill with blood. Every morning, she takes a loop diuretic to prevent fluid from building up in her lungs. At her three-month check-up, her potassium level is low again: 3.3 mEq/L. Her cardiologist adjusts her electrolyte replacement and considers the matter closed. But what no one is discussing is whether this chronic low potassium is pushing her toward a second diagnosis she doesn’t yet have: type 2 diabetes.

This scenario plays out in cardiology clinics every day. Heart failure affects more than six million adults in the United States alone, and about half of them have the form where the heart’s contraction function is relatively preserved^[2]. These patients are often older, frequently women, and burdened with comorbidities like obesity, hypertension, and prediabetes—a metabolic powder keg. A new study now suggests that low potassium may be the spark that ignites it.

What the Research Reveals

Researchers examined the relationship between hypokalemia—defined as a serum potassium level below the normal range—and the development of new-onset type 2 diabetes, specifically in patients diagnosed with heart failure with mildly reduced ejection fraction (HFmrEF) or preserved ejection fraction (HFpEF). The study found a significant association between low potassium levels and incident type 2 diabetes in this population^[1].

This is a clinically important connection for several reasons. First, the HFpEF and HFmrEF populations are already at high metabolic risk; adding hypokalemia to the equation may accelerate the progression from prediabetes to overt diabetes. Second, these patients are among the most frequent users of potassium-wasting diuretics—thiazides and loop diuretics—which are cornerstones of heart failure symptom management. The very medications that keep them out of the hospital for fluid overload may be silently eroding their metabolic resilience.

This hypothesis was examined in a cohort of 3,224 participants from the FINEARTS-HF trial who did not have diabetes at baseline (mean age 72, 47% women, and mean baseline potassium of 4.4 mmol/L) over a median follow-up of 2.7 years.^[8] Each 0.5 mmol/L decrease in time-updated serum potassium levels independently increased the risk of developing new diabetes by 19% (adjusted hazard ratio [aHR]: 1.19; 95% CI: 1.04–1.36). For those who experienced a lab-defined episode of overt hypokalemia with serum potassium dropping below 3.5 mmol/L, the risk of new-onset diabetes surged 2.07-fold (a 107% increase; aHR: 2.07; 95% CI: 1.33–3.22), with the incidence rising from 3.1 to 4.8 cases per 100 person-years. Moreover, this metabolic fragility was not just confined to the classic hypokalemia threshold; even in the “mild gray zone” where potassium dipped below 4.0 mmol/L, the diabetes risk increased by 37% (aHR: 1.37; 95% CI: 1.05–1.80).

The Mechanism: How Potassium Governs Insulin

To understand why a simple electrolyte imbalance might trigger diabetes, one must look inside the pancreatic beta cells—the tiny insulin factories clustered in the islets of Langerhans. Insulin secretion is, at its core, an electrical event. When blood glucose rises, glucose enters the beta cell and is metabolized, producing ATP. This ATP closes ATP-sensitive potassium channels (K_ATP channels) in the cell membrane, which causes the cell to depolarize. Depolarization opens voltage-gated calcium channels, calcium floods into the cell, and insulin-containing granules are released into the bloodstream^[3].

Potassium is the linchpin of this entire cascade. When extracellular potassium falls, the electrochemical gradient across the beta cell membrane changes. The cell becomes hyperpolarized—meaning it is essentially harder for the cell to “fire.” Even when glucose is abundant, the electrical trigger for insulin release is blunted. The result is impaired insulin secretion and, over time, chronically elevated blood glucose^[4].

There is also evidence that hypokalemia impairs insulin sensitivity in peripheral tissues like skeletal muscle and the liver. Animal studies have shown that potassium deficiency reduces glucose uptake in muscle, thus adding a problem of resistance to the defect in secretion^[5]. The combination of less insulin being produced and the insulin that is produced being less effective is a perfect recipe for diabetes.

This disruption at the cellular level is not confined to the pancreas; it also extends to major glucose repositories like skeletal muscle and liver. Low potassium alters the cell membrane potential, making it difficult for muscle fibers to take in glucose even when sufficient insulin is present in the blood, thereby adding peripheral resistance to the problem of inadequate insulin secretion. The first solution that comes to mind, classic potassium-sparing drugs (steroidal MRAs like spironolactone), have failed to prevent the development of new diabetes in large clinical trials, despite raising potassium levels. This suggests that metabolic protection is not merely about increasing serum potassium; it requires simultaneously targeting the chronic inflammation created by mineralocorticoid receptors at the tissue level.^[9]

The link between diuretic use and hyperglycemia has been known for decades. Landmark studies, including the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), noted higher rates of new-onset diabetes in patients treated with thiazide-type diuretics compared to those treated with other antihypertensive agents^[6]. Subsequent analyses suggested that much of this excess risk was mediated by diuretic-induced hypokalemia rather than a direct drug effect on glucose metabolism^[7]. The current study brings this understanding into the realm of heart failure, where diuretic use is not optional—it is essential for survival and quality of life.

Limitations to Consider

Without full details on the study’s size, design, and adjustments for confounding factors like body mass index, baseline glucose levels, and specific diuretic regimens, the strength of this association should be interpreted with appropriate caution. Observational data can identify associations but cannot confirm causation. It is possible that hypokalemia is a marker for more aggressive diuretic use, sicker individuals, or other unmeasured variables that independently increase diabetes risk. To establish a causal link, prospective, interventional trials would be needed—for example, randomizing heart failure patients to aggressive potassium repletion versus standard care and monitoring diabetes incidence.

The Final Verdict: What These Findings Mean for Tomorrow’s Patients

For the millions of people living with HFpEF or HFmrEF, this research carries a practical message. Potassium is not just a number to be kept above 3.5 mEq/L to avoid arrhythmias. It may be a metabolic vital sign, offering a modifiable window of risk for diabetes.

Clinicians managing these patients should consider more frequent potassium monitoring, especially in those with prediabetes, obesity, or a family history of type 2 diabetes. When diuretics are necessary, potassium-sparing agents like spironolactone or eplerenone—which already carry guideline-endorsed benefits in heart failure—may offer a dual advantage: neurohormonal blockade and metabolic protection. Dietary counseling on potassium-rich foods like bananas, spinach, and sweet potatoes can complement pharmacological strategies.

The FINEARTS-HF analysis also reveals an illuminating mechanism regarding the role of the non-steroidal mineralocorticoid receptor antagonist (nsMRA) finerenone in preventing new-onset diabetes.^[8] While finerenone alone reduced the risk of developing diabetes by 24% (HR: 0.76; 95% CI: 0.59–0.97), causal mediation analyses showed that only about 20% to 31% of this protective effect was attributable to its impact on raising potassium levels and preventing hypokalemia. In other words, nearly two-thirds of the drug’s metabolic shield is explained by direct mineralocorticoid receptor blockade and modulation of anti-inflammatory pathways in target tissues, independent of potassium. The fact that classic steroidal MRAs (like spironolactone) have not demonstrated similar success in preventing diabetes in large trials, despite raising potassium, further enhances the value of finerenone’s selective receptor effect in the pancreas and peripheral tissues.

For patients, the takeaway is clear. If you have heart failure and are on a diuretic, ask about your potassium level at every visit. A small number on a lab report may have unexpectedly large consequences for your metabolic future. Keeping potassium in the right range is one of the simplest interventions in medicine—and this study suggests it may also be one of the most important.

Scientific Sources

1. Ostrominski JW, et al. Hypokalemia and New-Onset Diabetes in Heart Failure With Mildly Reduced or Preserved Ejection Fraction. Diabetes care. 2026. PubMed: https://pubmed.ncbi.nlm.nih.gov/42663524/
2. Dunlay SM, et al. Epidemiology of heart failure with preserved ejection fraction. Nat Rev Cardiol. 2017. DOI: 10.1038/nrcardio.2017.65
3. Ashcroft FM, et al. ATP-sensitive potassium channelopathies: focus on insulin secretion. J Clin Invest. 2005. DOI: 10.1172/JCI25495
4. Rowe JW, et al. Effect of experimental potassium deficiency on glucose and insulin metabolism. Metabolism. 1980. DOI: 10.1016/0026-0495(80)90074-8
5. Helderman JH, et al. Prevention of the glucose intolerance of thiazide diuretics by maintenance of body potassium. Diabetes. 1983. DOI: 10.2337/diab.32.2.106
6. ALLHAT Officers and Coordinators. Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic. JAMA. 2002. DOI: 10.1001/jama.288.23.2981
7. Shafi T, et al. Changes in serum potassium mediate thiazide-induced diabetes. Hypertension. 2008. DOI: 10.1161/HYPERTENSIONAHA.108.119438
8. Butt JH, et al. FINEARTS-HF Committees and Investigators. Finerenone and new-onset diabetes in heart failure: a prespecified analysis of the FINEARTS-HF trial. Lancet Diabetes Endocrinol. 2025. DOI: 10.1016/S2213-8587(24)00309-7
9. Grodzinsky A, et al. The impact of cardiovascular drugs on glycemic control: a review. Endocr Pract. 2017. DOI: 10.4158/EP161309.RA